Field
This disclosure relates generally to wafer level packaging, and more specifically, to shielding signal lines in a redistribution layer of a wafer level package by using other metal layers.
Related Art
As wireless connectivity is expanded to more devices and the sizes of those devices are reduced, radio frequency (RF) devices are placed closer to digital and baseband packages. Digital and baseband packages can generate electromagnetic noise and interference that can disrupt or impair operation of RF systems. Digital circuitry and the power supplies for such circuitry can operate at frequencies of 500 MHz to 3 gigahertz. A single digital chip can have millions of switches operating at those frequencies and generating noise at those frequencies and harmonics of those frequencies. These frequencies can be close to the radio frequencies used by electronic systems for wireless communications. As a result, antennas, filters, multiplexers, modulators, up and down converters, and amplifiers or gain stages can all be impacted by the noise generated by a nearby digital chip.
As a result, RF devices (e.g., an RF modem) is typically shielded by a metal case that covers the RF device to avoid interference from the digital and baseband circuitry. But shielding the chip may not avoid RF signals transmitted through conductors in package interconnect redistribution layers (RDL) being affected by noise and interference transmitted in nearby RDL conductors or other nearby chips or packages.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The figures are not necessarily drawn to scale.